Drill screw

Abstract

A drilling and reaming screw is disclosed having a drill tip and a pair of frangible wings as a reaming means. The frangible wings are formed from the shank so that they include inner portions within the shank diameter and outer portions outside the shank diameter. Upon reaching a workpiece of predetermined hardness, the outer portions are adapted to break off from the shank along a line lying entirely beneath the surface of the shank such that no harmful protuberances remain.

I claim: 
     
       1. A drilling and reaming screw for use in fastening two or more juxtaposed workpieces, said screw comprising a drill tip, a shank having a surface defining a first radius, a head, a screw thread on a portion of the length of the shank, and two or more frangible reaming means projecting from a region of the shank intermediate the tip and the thread and pinched from the shank material, said projecting reaming means being integral with the shank and each including an inner and an outer portion, said inner portion extending radially inwardly from the shank surface to a juncture line which includes upper and lower segments, each segment intersecting the shank surface at an acute angle thereto, said outer portion extending radially beyond the shank surface to a radius at least as great as the crest radius of the thread being thereby operative in workpieces made of materials of less than a predetermined hardness to form a hole having a radius at least as great as the crest radius of the thread, but being so weakly connected to the shank that the reaming means will be broken and separated from the shank in workpieces formed of materials of more than the predetermined hardness, said separation occurring along a line lying entirely beneath the surface of the shank such that no harmful protuberances remain.